Determination
by Sherri3555
Summary: What if the Marauders, Lily, Severus and Regulus were trapped in a black room? What if they were to play Undertale, but with a big twist? Will be rewritten...eventually. Give me, like, a year.
1. Prologue

**Upon noticing that Sherri finally uploaded a fanfiction, it fills you with DETERMINATION.**

* * *

"Where am I?"

Lily Evans awoke at the sound of an annoying voice; one she's heard for the six years she's been at Hogwarts. She opened her eyes and examined her surroundings.

It was a cold black room, with no light at all.

James Potter, Sirius Black, Remus Lupin and Peter Pettigrew were laying around, with the three already awake and James just waking up.

Lily turned around and almost scowled at the sight.

Severus Snape and Regulus Black both were awake, looking at everyone else.

"WHAT THE HELL IS SNIVILLUS DOING HERE!?" Of course, that's the only thing that James Potter seems to worry about.

"Is that sincerely all that you worry about?" Severus hissed, glaring at the Seeker. "Do you think I enjoy being here with you, Potter?"

Sirius growled at the obsidian-eyed boy. "You better shut that mouth of yours or I'll rip out your tongue, Snivellus!"

Sirius went to reach his wand from his pocket, only to find it missing.

"Hey! Give back my wand!" Sirius yelled, glaring directly at the older Slytherin (older than Regulus, not Sirius [I think]).

"What makes you think that I stole it?" Severus said coolly.

"You Slytherins were the only ones awake! Clearly, you would be the only ones to take it!" James sneered, so sure of his logic.

Regulus spoke up softly, not wanting them all to result in a physical fight. "Remus was already awake before we were. Surely he would've witnessed us stealing any of your possessions."

' _Besides, what they don't know is that we don't have our wands either_ ,' Regulus thought.

"I didn't see any of them even go near us," Remus calmly stated to the two peeved boys. "Maybe someone else took it."

"I'll only spare you because Remus apparently didn't witness you two stealing, but we'll be keeping an eye on you two," Lily warned. She didn't have her wand either.

"N-none of us h-have wands?" Peter studdered. He's never been without his wand for years. He wondered if they'll ever get their wands back, or remain like squibs in a dark room forever with their worst enemy. The thought frightened him. He certainly did not want to stay with Severus, he was just pure cold and had a glare that always catched Peter off-guard.

"No," Lily answered, patting the pocket of her robe.

"Me neither," Severus replied, looking down on the ground.

Sure, it was nice and all to be here with Lily but those idiotic morons were there as well, and Lily was still pissed off at him for calling her the m-word. At least Regulus was decent, not harming Severus but not exactly friends with him either.

"Well, if none of us have wands, then we'll have to find another way to escape," Remus stated. "But, since we're here now, we're going to have to be civil towards one another. I'm not saying that we're all going to make up and become besties, but I suggest that we forget about our rivalry for a while until we escape. That way, we'll waste less time and perhaps find a way out more quickly."

Lily nods in agreement. "Remus is right. As much as I don't want to be here," she paused mid-sentence to glare at James, "there's no reason that we should be fighting when we have other things to worry about, such as why we're here and who kidnapped us."

"Speaking of which, what is that thing?" Everyone turned around to see Peter pointing at what looked like an odd-shaped device with colorful buttons on it. **(1)**

Just when they were about to respond, the device teleported into Lily's hands and stayed put.

"What the hell?" Sirius exclaimed. What was this strange thing that looks like a minature TV gone wrong?

"It's a controller," Lily stated, observing the device in her hand. "It's a Muggle object use to control some sort of game on a television screen. But if this controller is here, than where is the—"

Just before she finished her question, a giant screen in front of them turned on. Everyone squinted their eyes at such a bright light. The blinding light stayed for a few minutes before disappearing.

Everyone glanced at the screen, shock to see a completely black screen with the only thing there was white text.

 _*Select Your Character's Name_

"Hey," Peter asked, breaking the silence. "May I play?"

"Sure," Lily answered, handing over the controller to Peter. A spark of electricity zapped Peter, causing the Gryffindor to jolt back in pain.

"What the-"

"It seems like it wants for you to play," Remus said, glancing towards a teary-eyed Peter. "Are you alright Peter?"

"Y-yeah! Just a bit of pain, nothing major!"

Lily entered in her name silently.

 _*Um, you sure? There's a better name, you know? But okay, I'm not stopping you._

"What is that suppose to mean?" Sirius asked.

"A bit rude, isn't it?" James said, giving Lily a flirtatious wink. "I think 'Lily' is a perfect name."

Both Severus and Lily gave him a disgusted look.

"Stop your flirting, Potter," Lily hissed, pressing 'A' on the controller. **(2)**

Her name was zoomed in, with the letters shaking like there was an earthquake before the screen turned completely white.

Little did Lily Evans know, this game is no ordinary game. And little did she know, a potential " _ally_ " is the reason she made the worst choices.

* * *

 **When noticing that Sherri wrote about Undertale and Harry Potter in the same fanfiction, it fills you with DETERMINATION.**

 **1) X-box controller! Sorry PlayStation lovers, but I prefer X-box. Oh, and I know that the X-box didn't exist back then (did it?) but this is a fanfic so let it slide please. It's not like it's the holy weapon that's the key to ruling the world!**

 **2) I don't know crap about the controls since I don't own the game, but it's not going to be a key element in this story so I'm not going to search it up.**

— **Sherri3555**

 **P.S. Sorry but I can't upload a Valentines' Day fic, haven't even typed it out yet and I was busy with the exam I had taken just today. But you have a wonderful new series here, so I guess that makes up for that. Happy Valentines' Day!**


	2. Under His Wings (Part 1)

**Noticing that Sherri has written a long chapter, it fills you with DETERMINATION.**

 **Toriel =** _BlahBlahBlah_  
 **Flowey = BlahBlahBlah**  
 **White Text =** BlahBlahBlah  
 **SAVE** = (BlahBlahBlah)

 **Note: If you're a hardcore Undertale fan or you just remember some lines, you'll know that I literally copied the text for this run word for word.**

* * *

Lily opens her eyes, which she had squeezed shut.

Just after she entered her name, a bright light appeared and burned her eyes. She squeezed them shut to prevent the light from completely blinding her permanently.

Although rather than a dark room with the others, she was in some sort of ruin. The walls were all a dull gray with cracks and an ancient look to it. The concrete flooring was completely gray and with some cracks in it.

Lily was sitting on a bunch of buttercups, which was the only thing full of a lovely color.

Above her was a the sky, so far up. It looked orange, the sign of either the sun setting or rising.

From what it looked like, it was almost like she fell down a giant hole. But how could she have survived? And why did she fall in the first place.

She patted the flowers. To her surprise, there was a small black box in front of her, surrounded by white. It was thin as paper, and very small. Slowly, a small noise that made a weird robotic noise for a moment. White text formed as the sound continued, stopping after the noise stopped.

*The flowers must've broken your fall.

 _'How odd,'_ she thought. At least one of her many questions were answered. She looked down at her clothes and gasped.

Rather than her robes and school uniform, she had on a giant blue sweater with two pink stripes, a black skirt and dark brown hiking boots. Looking closely, she discovered that she felt . . . small. Peering at her hands, she almost gasped on how tiny they were. She stood up and noticed how close the buttercups were to her knee-caps. Did she—did she get shorter?

She peered at the box again.

*You feel strange.

She sure did.

 _'I—I don't know what's happening. Something must be wrong!'_

" **Determination** " is the only word in her mind. Why? What does determination have to do with anything?

It's just a feeling; it's just about wanting to move forward—right!?

She got up slowly, still not sure what to do. What is going on? Where is everyone right now? Why is she here?

It's all so confusing.

She glanced to see if there was any other way out.

There was no use going above—there was nothing she could easily climb onto. All she could do was move on.

She walked slowly, listening to her soft steps as they echo. The place wasn't like a sewer, but it had the feel of one. She went through what looked like a gateway.

 _'It's so dark in here,'_ she thought, looking around at the black room.

Suddenly, that robotic noise was back, but it sounded different. More annoying, actually.

In front of her was a small ray of light, like a spotlight. In the middle of the light was a . . . a flower? It was just a regular yellow flower . . . with a face. Okay, that's completely out of the ordinary, even for the wizard world.

 _'I don't remember learning about those in Care For Magical Creatures,'_ she thought. _'Then again, I doubt that wizard-kind knows where this weird place is.'_

 ***Howdy!**  
 ***I'm FLOWEY!**  
 ***FLOWEY the FLOWER!**  
 ***Hee hee hee...**  
 ***Why'd you make me introduce myself?**  
 ***It's rude to act like you don't know who I am.**

 _'But I don't!'_ she wanted to scream, but her words were silent. Her mouth didn't open at all.

 ***Someone ought to teach you some proper manners.**  
 ***I guess little old me will have to do.**  
 ***Ready?**  
 ***Here we go!**

Lily felt herself slowly floating in the air. She wanted to scream in fear, but her mouth refuses to listen to her.

The room around her became completely black. She looked down at her clothes and was surprised to see only black and white. Not black and white as in just seeing shades of gray, but literally only black and white. Outlining her body was a weird white line.

The only color she could see was the red heart floating in the air, just a few inches away from her heart.

She looked at Flowey, who was also in black and white.

The box in front disappeared, only to be replaced by another box. The box showed the red heart trapped in a white outlined box. Below the box said this:

*LV 1

*HP 20/20

Just between the 'HP' and '20/20' was a small, yellow bar. Lily wondered what it could possibly mean.

 ***See that heart? That is your SOUL, the very culmination of your being!**

 _'How interesting,'_ she thought, staring at the red SOUL. _'But why does it matter? Besides the fact that it's like my actual soul.'_

 ***Your SOUL starts off weak, but can grow strong if you gain a lot of LV.**

 _'LV?'_

 ***What's LV stand for? Why, LOVE, of course!**  
 ***You want some LOVE, don't you?**  
 ***Don't worry, I'll share some with you!**

Flowey winked at Lily, sticking his tongue out.

For some reason, Lily found it quite insulting that he even did that. Perhaps it was because it reminded her of Potter, the dimwit. At least Flowey was bearable.

 ***Down here, LOVE is shared through...**

While he spoke, little white pellets were hovering in the air in a circle formation. They looked threatening, but then again, she was talking to a dumb flower with a face.

 ***Little white... "friendliness pellets."**

 _'That doesn't sound right at all,'_ Lily thought, slowly getting more and more uneasy with this odd... creature? Monster? Yes, monster sounds just about right.

 ***Are you ready?**  
 ***Move around! Get as many as you can!**

Although Lily didn't exactly trust him, she did want to have love.

 _'I wonder why it's capitalized like that. How odd.'_

Doing as she was told, she found herself able to control the red heart. The pellets started heading towards her heart. Trusting Flowey, she quickly grabbed all of them when a shocking pain came. Her chest, it hurted so much!

Clutching herself, she looked at the HP bar. It was all red, with a 1/20 replacing the 20/20.

 _'What's going on? Flowey, what did you do!?'_

Flowey just stared at her. His expression changed completely. Rather than the innocent face he had before, it was a face of cruelty and pure evilness. Black, soulless eyes stared directly at her. His smile was large, with all of his sharp teeth shown. He was smiling—no, _laughing_ at her.

 ***You idiot.**  
 ***In this world, it's kill or BE killed.**  
 ***Why would ANYONE pass and opportunity like this!?**

Lily stared in shock at the flower. How could he betray her trust?

 _'I should've known that he'd do this,'_ Lily thought, glaring at Flowey. _'The moment he said 'friendliness pellets', I should've been skeptical.'_

Lily watched as multiple pellets formed in a tight circle around her heart, slowly closing in on her. She was trapped!

 ***Die.**

He sounded so mean.

She stood still, unable to do anything. She was paralyzed, stuck in place. Her mind was blank and all she felt was betrayal. How could he?

Closing her eyes, she awaited for the pain.

 _But nothing came._

She opened her eyes. Flowey was normal now, but with a mixture of surprise, annoyance and anger in his face.

The pellets were nowhere to be seen and her bar was completely full. It was 20/20 again.

The two surprised people—monster in Flowey's case—stared at each other in shock, unsure of what to do.

Suddenly, a fire ball shot through the room, smacking Flowey directly in the face.

Flower glares at Lily for a moment before popping down (that's a weird way to phrase that), retreating from who-knows-what.

The world flooded with color.

 _*What a terrible creature, torturing such a poor, innocent youth._

Lily looked up.

A older-looking James Potter smiled at her. But he looked...different.

He looked a lot more mature-looking. His eyes were cold black, with no mischievous glint in those soulless eyes. It was like looking into Severus—er, Snape's eyes. His skin was pale, not the tan skin James always had from playing Quidditch so much.

But the most striking feature was his hair.

Sure, it still had the messy look to it. But it was like a more natural kind of messy, a slightly bit more neater and mature-looking. But it was completely white, like it was completely bleached. When Lily looked more closely, she was surprised to see small horns on top of his heads. His teeth was completely sharp and his mouth looked slightly longer than a normal human's. Two teeth were poking out, like fangs. He looked funny.

He didn't wear any of his usual clothes, but rather, a large purple hoodie with a odd looking blue and white symbol on it. His hood and his sleeves were a much lighter shade of purple, like a lilac color. He wore light gray jeans and white sneakers.

It was like he gotten even more taller than before, but perhaps it was because she was shorter than she was when she was in her sixteen-year old body.

 _*Ah, do not be afriad, my child._  
 _*I am TORIEL, caretaker of the RUINS._

Toriel smiled kindly at her.

 _'How is this James? The James I know is a complete git, but he is so...mature! What's wrong with me? Or better yet, what's wrong with him?'_

 _*I pass through this place everyday to see if anyone has fallen down._  
 _*You are the first person to come here in a long time._  
 _*Come! I will guide you through the catacombs._

He held out his hand at Lily. Although she didn't really want to, something deep inside her presued her to accept her hand. **(7)**

 _*This way._

Toriel guided her to another room, a room with purple brick walls and a matching purple floor. There were weird shades of purple, oddly in a very specific shape and place.

Slowly, Lily follows as Toriel led him to the end of the room. He let go of Lily's hands, turning around to give a small smile.

At the end of the hall was like a gray/really light and dull purple stage. There were a stair up at each end, with a bed of rose petals in between. The area that Lily was standing, where the purple floor was slightly lighter with a darker circle in the middle, rose petals outlined the rectangle, separating the light from the darker flooring. (That's gotta confuse you.)

Lily perked up at the sight of a glowing star, which Toriel seemed to ignore. He walked up the stairs and turned around, waiting for Lily.

Lily headed towards the star when her black box appeared again.

*(The shadows of the ruins looms above, filling you with determination.)  
*(HP fully restored.)

 _'That's odd,'_ she thought. Filled with curiosity, she looked up and noticed the shadows. It didn't seem inspiring at all, but rather, just ... dull.

Lily looked at her box again.

 **EMPTY LV 0**  
 **_ _**

 ***Save *Return**

 _'That's odd, never seen that before. What is this star anyways?'_

She reached out and hit the SAVE button.

Yellow text appeared, replacing the white text.

 **Lily LV 1**

 **Ruins - Entrance**

 **File saved.**

Lily nodded in satisfaction.

 _'So it's like a save point in my progression in this world. Like a game. Maybe that's why there was a controller and a giant light.'_

And that's when realization hitted her.

 _'I'm in a game!'_

Lily found herself following Toriel, but she just couldn't keep her thoughts from clouding up her mind. The question just kept on flooding in: 'Why am I in a game?'

 _*Welcome to your new home, innocent one._

 _'Don't call me that. I'm not your average child, James. I will never be your girlfriend, so stop trying to act like you care for me "as a child." I know you're act, you're in the game too, aren't you? You aren't very clever, you jerk.'_

 _*Allow me to educate you in the operation of the RUINS._

 _'What an idiot, thinking he can keep me so safe. I bet he doesn't even know how the ruins even operate. Doesn't seem like the type to memorize anything.'_ Lily tried to scowl, but her body refused to follow her order. Instead, she looked at the ceiling.

 _'Sure is high,'_ she thought. She looked back down and watched Toriel step on all of the buttons on the floor except two. Then, he pulled the lever.

Lily watched in amazement as the doors open by itself.

 _*The RUINS are full of puzzles._  
 _*Ancient fusions between diversions and doorkeys._  
 _*One must solve them to move from room to room._

 _'I think I can take care of myself,'_ Lily thought. _'I'm an independent woman, one who can easily overcome simple puzzles.'_

 _*Please adjust yourself to the sight of them._

 _'What? I can take care of myself, Toriel. No offense, but I don't need a guide.'_

Unable to hear Lily's thoughts, Toriel awaited for her to follow him to the next room. Lily, helpless, trailed behind.

The purple hallways was extremely large and long. Up ahead, there was were streams of water coming from pipes that covered the entire floor. The only way across these streams was a bridge without railings. There was the occasional vines growing on the cracks on the wall, as if it was completely normal.

 _'Definitely not child-proof,'_ Lily thought as she absorbed the scenery.

 _*To make progress here, you will need to trigger several switches._  
 _*Do not worry, I have labelled the ones you need to flip._

Toriel took Lily's hand and guided her through the room. In the middle of the room, he paused and faced the lever. It was clearly labelled, with arrows pointed at the switch.

Lily went over and pulled it. At first, it was a struggle, but she had the strength and determination to pull it.

They walked along until they reached the end of the room. The only thing preventing them from continuing to the next room was spikes completely blocking the doorway.

Two levers were on the wall, the left on clearly labelled.

Lily pulled the left one.

 _*Splendid!_  
 _*I am proud of you, little one._

 _'Little one?'_ Lily thought. She really wanted to scowl. As much as Toriel seemed nice and mature, it was hard to look at him when he looked so much like James Potter, a complete idiot compared to Toriel.

Plus, you never know if Toriel is just like Flowey. That stupid flower helped her out at first, then tried to kill her!

 _*Let us move to the next room._

Toriel entered the next room. Lily paused, trying to figure out what to do now.

 _'Do I really want to follow him?'_ Lily pondered, staring blankly at the stream of water.

Lily proceeded to walk to the next room. _'Not like I really have much of a choice,'_ she thought as she slowly walked. 'He could simply conjure up some fire and blast me to ashes if I don't do as he says.'

The next room wasn't a hallway, but like a small corner for people to hang out and chat. However, the only thing in the room was a dummy, an oddly shaped dummy to be exact.

 _*As a human living in the UNDERGROUND, monsters may attack you._

 _'What!?'_

 _*You will need to be prepared for this situation._  
 _*However, worry not!_  
 _*The process is simple._  
 _*When you encounter a monster, you will enter a FIGHT._  
 _*While you are in a FIGHT, strike up a friendly conversation._

If Lily had complete control over her body, her jaw would be hanging open. Talking while you're in a fight? That will get you completely killed!

 _*Stall for time. I will come to resolve the confict._  
 _*Pratice talking to the dummy._

 _'Yeah right!'_ Lily hissed in her mind. _'Monsters will be eating my flesh by the time you rescue me!'_

Now for those who are familiar with Undertale, you may already know the path Lily will go to. You might be thinking, _'Why did you make Lily go the the *blank* path?'_

Think about it. This is James, the boy Lily Evans hated since Day 1. Sure, he may act different, but six years of rejecting James has almost become a habit for Lily. And you have to admit, talking to monsters? That doesn't exactly sound quite right, especially after talking to Flowey didn't do crap.

Now you see? Lily has been trained for six years how to defend herself from monsters, and she didn't have any magic she could use to defend herself. Which means plan B; the old-fashion Muggle way of protecting themselves.

Toriel stood in front of the doorway, blocking any escape route. Not that there was much to escape from, anyways.

Lily walked over to the dummy and the black and white returned. However, this time, four buttons appeared in front of her. Her soul appeared once more, shining brightly.

*FIGHT  
*ACT  
*ITEM  
*MERCY

She clicked the logical one, the one she felt wasn't nonsense compared to the rest.

 ***FIGHT**

She tapped the FIGHT button.

*Dummy

Next to 'Dummy' was a long, green bar. Lily assumed that it was his health bar. Or was it a her? Or an it?

Whatever.

She tapped the text and watched as a odd pattern appeared. She had a moving white bar hovering over the pattern. When the bar was at the middle, she immediately punched the box.

A red, pixelated dash swiped over the dummy. The dummy crumbled into dust, which slowly started to disappear.

*YOU WON!  
*You earned 0 XP and 0 gold.

The world started to turn back to it's usual color. Lily felt quite relieved that it was gone.

That dummy just had that stare. Just a stare. Like...a stare.

Lily honestly thought it would be a bit more tougher. Apparently, dummies turned to...dust? Okay, physics definitely didn't apply in this game.

Toriel stares at Lily with a disappointed frown on his face.

 _*Ahh, the dummies are not for fighting!_  
 _*They are for talking!_

 _'Sounds like a dumb excuse for a dummy if you ask me,'_ Lily mentally sneered.

 _*We do not want to hurt anybody, do we...?_  
 _*Come now._

Toriel led Lily to another room. It was a hallway, with a bunch of vines on the wall.

 _*There is another puzzle in this room..._  
 _*I wonder if you can solve it?_

 _'Of course I can! Wait, are you implying that... are you implying that I cannot solve a simple puzzle!?'_ she mentally screamed.

He led her down the hallway, careful not to accidentally go too fast for Lily's small feet.

Lily followed Toriel, now bored with the same old process. Toriel solves the problem for her or makes it so easy, then they progress and do it again.

She almost missed the sight of a frog in front of her. Quickly, like the dummy fight, the world turned black and white.

It was a frog, an odd looking frog for sure. It was obvious that it was a frog, but something was off about it...was that a face on the belly of the frog!?

Her health bar, LV and four buttons appeared.

*Froggit attacks you!

Lily glared at the frog in front of her. How dare that monster try to fight her!

She pushed the FIGHT button and smacked the text that said Froggit.

The patterns returned once again, but this time, Lily was not hesitant to make a critical hit. She eliminated the frog in seconds and watched as a) the dust spreaded to her clothes and b) the monster disappeared the same way the dummy did.

*YOU WON!  
*You earned 10 XP and 20 gold.  
*Your LOVE increased.

Lily managed to take somewhat control of her body and smirked proudly. She made a mental note to kill every monster down here.

Now you might be wondering: why?

It was a Gryffindor-ly thing to do. After all, it was all in the name of justice. Lily thought that she was saving human kind by protecting them from big bad monsters! And logically speaking, it was actually pretty reasonable.

The world flooded with color, with the white-haired man frowning at him. However, he said nothing about it and just kept walking.

That's when they reached the room with the floor surrounded by deep water. There was a bridge, which led to...

A bunch of spikes.

 _'How do you get across that!?'_ she thought. It looked impossible, with the spikes to high for Lily to get across. And too many to get by very easily as well.

Toriel turned around with a caring smile. Lily hoped that they were not going to cross the spikes, although she knew that they were going to go straight through them somehow.

 _*This is the puzzle, but..._  
 _*Here, take my hand for a moment._

Reluctantly, she obeyed.

Toriel led her through the spikes. As they walked through, the spikes lowered to make a clear path for them to walk. It followed a weird pattern, but Lily felt that it probably had to do with a sign she should've read.

When they reached the end, Toriel turned around.

 _*Puzzles seem a little too dangerous for now._

They entered the next room, which was a seriously long hallway.

 _*You have done excellently thus far, my child._  
 _*However...I have a difficult request to ask of you._  
 _*..._  
 _*I would like you to walk to the end of the room by yourself._

Toriel had a sad smile.

 _*Forgive me for this._

Quickly, Toriel rushed away to the end of the room.

Lily tried to keep up, to see why he was so nervous about walking to the end, but she couldn't keep up with the older man.

 _'Wow, that sounds so weird in my head,'_ Lily thought, a bit uneasy with the fact that the James in this world was a lot older than her. This meant that she had to respect James, didn't she?

 _'What an awful thought.'_

* * *

 ***(Curious with what Sherri has planned next, it fills you with DETERMINATION.)**  
 ***(Leave a review about what you think and any critics to save your file!)**

— **Sherri3555**

 **Note: I wanted to updated this since I put a lot of effort into this. Unfortuanetly, I planned for this to be extremely longer than this chapter. So I decided I needed to splitted these kinds of chapters so I won't be leaving you guys hanging. To think, this chapter is shorter than the ones planned in the future...**


End file.
